Fingerprints Flashcards
(22 cards)
What is the difference between a fingerprint and a fingermark?
A fingerprint is a clear ridge impression from deliberate contact, while a fingermark is often smudged or incidental.
What are latent prints?
Invisible fingermarks that require development to be seen.
What glands contribute to latent print composition?
Eccrine (sweat), sebaceous (oils), epidermal sloughing, and apocrine (minimal).
What are the two main components in a latent fingerprint?
Aqueous (water, salts, amino acids) and lipid (fatty acids, cholesterol) components.
How does a latent print change with time?
Water evaporates, the print becomes brittle/waxy, and visualization becomes harder—best collected within 2 weeks.
What environmental factors affect latent print quality?
Temperature, humidity, airflow, light, surface type, and time.
What is the first step in latent print development?
Examination under forensic light sources.
Which surfaces are suited for powder dusting?
Smooth, non-porous surfaces.
What does ninhydrin react with in a latent print?
Amino acids, producing Ruhemann’s Purple.
Why is ninhydrin useful for forensic analysis?
Non-destructive and compatible with DNA recovery.
What types of fingerprint powders exist?
Black carbon, metallic powders, and luminescent dyes (e.g., Rhodamine).
How does superglue (cyanoacrylate) fuming work?
Vapor polymerizes on lipid residues, forming a durable white print.
What improves visibility during superglue fuming?
Humidity/moisture in the chamber.
Who developed the original fingerprint classification system?
Sir Francis Galton (1892)
What are the three basic fingerprint patterns and their population frequencies?
Loops (60%), Whorls (34%), Arches (6%)
What makes a fingerprint unique?
The specific arrangement of ridge characteristics (~150 per print)
What is individualization in fingerprint analysis?
Determining that two prints came from the same source based on friction ridge detail.
What is AFIS?
Automated Fingerprint Identification System—digitally compares and stores fingerprints but still requires human verification.
What advanced chemical technique can determine donor age from a fingerprint?
FTIR (Fourier-transform infrared spectroscopy), based on lipid concentration.
What chemical method can detect race or gender from fingerprints?
GC-MS by analyzing fatty acid ratios.
What is LADI-MS used for in fingerprint analysis?
Detecting exogenous materials in fingerprints (e.g., drugs, cosmetics) via laser ablation imaging.
What are the five criteria for fingerprint individualization according to OSAC?
Sufficient detail, same area, reproducibility, absence of discrepancy, competent examiner
